GB1050446A - - Google Patents

Abstract

1,050,446. Rectifying. WESTERN ELECTRIC CO. Inc. June 20, 1963 [June 21, 1962], No. 24566/63. Heading H2F. [Also in Division G3] In a controlled rectifying circuit there are two transformers, the primary of one is connected directly to the alternating current supply, the primary of the other is connected to the alternating current supply through a controlling device and the outputs of the two transformers are combined together and then rectified. With this arrangement the range of output voltage control is limited (Figs. 6a and 6b, not shown) but some of the rectifiers can be cheaper, uncontrolled elements. The transformers T1, T2 (Fig. 1) are both fed from the alternating current source 10, 12, transformer T1 being fed directly while transformer T2 is fed through the controlling device 38. The outputs of the two transformers are combined, one end of secondary winding 15 of transformer T1 being connected to the centre tap of the secondary winding of the transformer T2, so that the current provided by the transformer T1 does not induce any voltage in the primary of transformer T2 which might damage the controlling device 38. The combined current is rectified by the six rectifier elements shown and passed through smoothing choke 28 to the output terminals 30, 32. The controlling device 38 may be driven by a control circuit 34 which measures the voltage or current in the direct current circuit. The controlling device 38 may comprise a semi-conductor controlled rectifier connected across a bridge of diodes the other diagonal of the bridge being in series with the transformer T2 (Fig. 2a, not shown). Alternatively a pair of reverse parallel connected semiconductor controlled rectifiers or a saturable transformer may be used (Figs. 2b and 2c, not shown). In the arrangement shown in Fig. 4 the secondaries of the two transformers are connected in series to a simple bridge rectifier. Transformer T2 has two primaries 80, 81, each primary being connected to the supply through its own controlling device. The arrangement is such that with one controlling device the voltages in the transformer secondaries are added but with the other controlling device the secondary voltages are subtracted. A suitable magnetic amplifier firing control circuit for this embodiment is described (Figs. 7a and 7b, not shown). Polyphase arrangements of both embodiments are described (Figs. 3 and 5, not shown).